Any Leaf Spring Technicians out there?

Submitted: Sunday, Mar 22, 2015 at 18:51
ThreadID: 117178 Views:2659 Replies:6 FollowUps:8
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Question for the knowledge bank...

I am building a light duty on-road trailer similar in design to an Ezy Trailer folding trailer. I have an issue with the leaf springs.

I have come into the possession of a pair of new trailer type leaf springs which the previous owner had no use for and didn't mind me obtaining them (true!). The trailer they would have been used for is a dual axle and rated at 1500kg loaded, hence the springs are safe for 750kg per pair, perfect! BUT they are as stiff as anything! Crazy stiff. Rock hard. Hard enough that their stiffness and the usual bouncing on the road may damage the folding parts.

They are four leaves. No 1 is the top leaf, eye to eye. No 2 is shorter, No 3 shorter still and with the riveted clamp devices, and No 4 is the shortest leaf and is retained with the centre bolt. I have replaced this bolt and removed (but kept) No 4 leaf. Leaves are about 5mm thick and the spring is 50mm wide.

My question is, what leaves should I remove to soften the spring pack? Reducing the capacity isn't a problem, the trailer won't be rated to 750kg loaded when I comply it.

I can safely dismantle the remaining leaves at work without damaging the heat treatment of the leaves.
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Reply By: Peter_n_Margaret - Sunday, Mar 22, 2015 at 19:04

Sunday, Mar 22, 2015 at 19:04
If the loaded weight will be under 750kg and it is for bitumen use only, I would probably opt for using identical wheels and tyres that you use on the car and not have any springs at all.
That would save another BIG pile of weight.
It will bounce about a bit, but there is plenty of "spring" in the tyres.

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AnswerID: 551413

Follow Up By: Bigfish - Sunday, Mar 22, 2015 at 19:38

Sunday, Mar 22, 2015 at 19:38
1500kg are way too much. If it is only for a really light weight trailer then the no-spring approach with a couple of wide tyres would work. You would want a wide tyre so as you get some sort of shock absorption. What about a single leaf spring? Have used them before on motorcycle and garden trailers with no issues. Plenty of boat trailers use them too.
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Follow Up By: IronMan - Sunday, Mar 22, 2015 at 20:17

Sunday, Mar 22, 2015 at 20:17
1500kg for FOUR wheels, FOUR springs. I have only two.
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Reply By: Ron N - Sunday, Mar 22, 2015 at 19:37

Sunday, Mar 22, 2015 at 19:37
IronMan - If you are building a light duty trailer, just the top leaf will probably be adequate.
Remove leaves starting from the bottom first and work your way up with the leaf removal until you have the right amount of springiness for the load you envisage.

Cheers, Ron.
AnswerID: 551415

Reply By: pop2jocem - Sunday, Mar 22, 2015 at 19:39

Sunday, Mar 22, 2015 at 19:39
Peter's advice sounds reasonable but personally I would be like to know what weight and exactly what type of load you intend carrying before recommending doing away with the spring packs altogether.

Also don't forget that leaf springs rely on the friction between the leaves for dampening so if the load is very light and you remove too many you are going to get a lot of bouncing happening which may or not be important depending on what you are transporting.

AnswerID: 551416

Follow Up By: Bob Y. - Qld - Sunday, Mar 22, 2015 at 19:47

Sunday, Mar 22, 2015 at 19:47

Agree with Pop about lack of dampening with only one leaf.

Something like these items, with one leaf, might be the go. Have used them before, and they seem to work alright.


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Follow Up By: IronMan - Sunday, Mar 22, 2015 at 20:35

Sunday, Mar 22, 2015 at 20:35
After reading the replies (thank you all!) I should have given more information.

The "folding special" is more just a project, but I want it to WORK. It will be only used to carry "stuff", lawn clippings to the tip, a couple of hundred kilo's on holidays on-road. As well as the springs, I also already have wheels and tyres, 6.00x9" 6 ply, sometimes found on boat trailers. 13" Holden or similar would have been ideal but when they're free...

My in-use 7x4 box was also built by me and it's a testimony that IronMan tends to over build things. The bloody thing is indestructible, but it's also heavy and a bit over-trailer for what i'll use it for. So when I finish my project I'll sell it.

For the project, I have bought the correct front and rear spring hangers and a light duty axle, and have hubs and bearings.
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Follow Up By: Life Member - Terry 80FTE - Sunday, Mar 22, 2015 at 21:07

Sunday, Mar 22, 2015 at 21:07
Name like "IronMan" you should know about suspension ;)
You are probable best to build it using the springs as is, load it to your capacity and test tow/bounce it to see how it performs.
It would help to know the spring length, we'll start by assuming (dangerous) about 800mm
If to tight, then remove no.3 leaf first and retry,
I prefer softer springs, but with shockers and bump stops.
With little wheels you'll need to keep an eye on the wheel bearings and tyres.
Good luck with your project,

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Follow Up By: Life Member - Terry 80FTE - Sunday, Mar 22, 2015 at 21:11

Sunday, Mar 22, 2015 at 21:11
Oh! and as you may need to shorten the centre bolt as you remove leaves, then you'll need new ones to add the leaves again if not happy.
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Reply By: Batt's - Monday, Mar 23, 2015 at 12:00

Monday, Mar 23, 2015 at 12:00
I don't know about the idea of not using springs that's pretty poor advice you'll need wide mirrors to watch your trailer bouncing down the road smacking into cars passing you and why would you want to jar the hell out of your trailer and it's contents just to save weight steer clear of that idea. All you can do is remove one leaf at a time till you find the ride that suits what you're after and make sure the spring hanger is not straight up and down should be at a minimum of 5 deg leaning back towards the axle. And use the correct tyre pressures to suit what you're carrying and let the springs do the work that they were designed to do not like the previously mentioned fellow who probably runs 10 psi to account for his lack of springs.
AnswerID: 551452

Reply By: Ron N - Monday, Mar 23, 2015 at 12:17

Monday, Mar 23, 2015 at 12:17
Batts is right, 6.00 x 9 tyres have no decent amount of sidewall to accommodate a "no-spring" style of construction.
If the tyres were much larger diameter with a high aspect ratio, you could consider eliminating springs.

The biggest problem here is that those 6.00 x 9 tyres are not really weight-carrying tyres, nor are they highway-speed tyres for any length of time.
So I trust the design use is only short local trips at below highway speeds.

Cheers, Ron.
AnswerID: 551453

Follow Up By: swampfox - Monday, Mar 23, 2015 at 13:04

Monday, Mar 23, 2015 at 13:04
You would be better to down rate a 6 x 4 than to build a """very limited micro trailer """

The end use u describe around a 300-400kg capacity .
Around 500-600 kg gross weight

The 6x9 tyres are ""speed limited ""

The better 6x9 are expensive as a 13 inch tyre .
There are good and bad brands of tyre in the 13 inch
The brands of tyre for 6x9 are lucky to be of average quality
A 13 inch trailer tyre is far easier to source on a long trip

There are 2 types of 6x9 type rim
1 with the bearings that sit in the rim
never ever use these
2 a rim that requires a separate hub bearing hub

Better off building a 39mm round axle
hq bearings /hq stud pattern
13 inch rims
3 leaf ,springs
The top leaf carries most of the load
The middle carries some of the load
The base or secondary limits the movement under max load conditions and depending on its design also help with weight carrying

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Follow Up By: swampfox - Monday, Mar 23, 2015 at 13:16

Monday, Mar 23, 2015 at 13:16
hi Ron N

Appologies hit the wrong button

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Reply By: swampfox - Monday, Mar 23, 2015 at 13:39

Monday, Mar 23, 2015 at 13:39
Use 40x40 x2mm wall and 50x50 2mm wall thickness Galv inside/outside
U can use 1.6mm wall thickness for above but its a lot easier to mig weld 2.0mm
Use 1.6mm sheet for the floor either gal or zinc
Use 65x 35 x 3mm wall for the draw bar
I would consider this good average sizes for a medium duty trailer

NB carrying grass or any corrosive green waste will cause corrosion at the welds in quick time . This is why I would use 2mm wall thickness .Thickness of material gives longevity .


AnswerID: 551457

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